Alarm testing and backup for implanted medical devices with vibration alerts

ABSTRACT

Alarm tests are disclosed which use alarm test signals to assess alarms provided by medical devices. Especially relevant are implanted devices that monitor cardiac activity and provide notification in response to medically relevant events. Alarm tests can occur periodically, or in response to a patient, doctor, or remote party initiating the alarm test. Alarm tests can also occur during the actual alarms issued to detected medical events. Alarm tests lead to pass or fail results, which in turn may cause operations to contingently occur. Alarm test failure in the auditory, visual, or tactile modality, may cause an alternatively defined alarm signal to be used as back-up. Alarm test logs can store alarm test results, including quantification of the measured alarm signal. Rapid alarm tests are described, as are various methods of accurately measuring characteristics of the test signal in ambulatory patients, which are especially relevant to a vibration alarm.

FIELD

The invention is in the field of implantable medical devices thatprovide patient notification. The invention is particularly relevant toimplantable cardiac devices that emit vibration alerts when selectedcardiac conditions are detected.

BACKGROUND

Implantable medical devices that monitor ambulatory patients must have amanner of alerting patients to relevant events. Notification can occurfor the detection of medical events such as acute ischemia, arrhythmia,bradycardia, or low levels of insulin. Notification can also betriggered by the detection of low battery levels, device malfunction,signal quality issues, and when device adjustment is merited. In orderto provide patient notification the implanted medical device (IMD) canuse either internal or external alerting means, or both. In the case ofinternal alerting, the IMD can use, for example, vibration or sonicalert signals. In the case of external alerting signals, the IMD maycommunicate with an external device which then produces an alert signalsuch as a vibrotactile, sonic, or visual signal. Multimodal alertprotocols occur when the alert signals are emitted to relay informationto multiple sensory modalities.

It is useful to provide both internal and external alerting for medicaldevices because this increases the likelihood that the patient will payattention to the alert signal and take appropriate action (e.g., goingto the hospital in the case of an emergency alarm related to a dangerouscardiac condition). However, in the daily life of a patient the IMD maynot always successfully communicate with the external device. Forexample, the patient may leave the external device beyond the IMDwireless communication range. Additionally, when the patient is in theshower or swimming an external device is not practical and alert signalsmay not be noticed by the patient. Further, the external device may notwork correctly as may occur if its battery becomes depleted. In thesecases it is important that at least internal alerting is available tonotify the patient to a serious medical event. Accordingly, it isimportant to be able to determine that the IMD can successfully providealerting to the patient.

Vibration alarms have a number of advantages. In the case of bothinternal and external alarms, patients may prefer relatively silentvibration alarms over sonic alarms that may cause persons nearby tolearn about a particular medical condition which is being monitored. Ina movie theater visual and auditory alarms may be inadvertently ignoreddue to saturation of these sensory channels, while there is littleinterference with respect to noticing a vibration alarm.

Alert transducers may fail in several manners. This is particularly truein the case of a vibration alert which requires moving parts. Atransducer may simply fail to operate or may operate in a compromisedmanner. In the case of vibration, the vibration may be provided at alower vibration level or frequency than intended. If an electric motorthat provides the vibration is not able to product the expectedstrength, frequency, or pattern associated with the alert signal, thenthe patient may misinterpret the alert, become unsure as to whether analert is occurring, or simply not experience it at all. Accordingly itwould be an advantage to provide a manner of objectively testing theintegrity of alarm signals such as vibration alarms.

Subjective reports of vibration have a number of disadvantages. Olderpeople or diabetics may experience lower levels of vibration due tophysiological factors rather than to actual mechanical changes whichoccur in the motor. If the patient complains that a vibration alarm isnot strong enough, a medical professional may pursue different solutionsdepending upon whether the problem is with the patient or the implanteddevice. Accordingly would be an advantage to provide a manner ofobjectively assessing the strength of the alarm signals such asvibration alarms.

Additionally, if a patient fails to respond to an alarm such as when thepatient is sleeping, the medical professional may not be able todetermine whether the alarm strength was inadequate for the patient andmust be increased, or whether the IMD did not actually vibrate asanticipated (or at all!) at the time of the alarm. It would be anadvantage to provide a manner of objectively determining if an alarmoccurred, and that it occurred as intended, at the time that the actualalarm was triggered. An alarm log of what actually occurred can bevaluable both for clinical and legal reasons.

Lastly, when changes in alarm characteristics are small, and alarmsoccur infrequently (e.g. not more than every 5 months) then a patientmay not be able to subjectively assess whether the vibration alarms havechanged from how they originally experienced these. Vibrotactilesensitivity for internal vibration signals changes as a function ofvibration pattern, frequency and amplitude. It is important to be ableto accurately measure any changes which may occur in the IMD's vibrationsignals so that these can be detected, quantified, and/or compensatedfor if desired.

The IMD can be any type of implantable medical device. In one embodimentthe IMD is a cardiosaver device, as described by Fischell et al in U.S.Pat. Nos. 6,112,116, 6,272,379 and 6,609,023, incorporated herein byreference, which can detect a change in the patient's electrogram thatis indicative of a cardiac event, such as acute ischemia and thenprovide notification. The IMD can also be a medical device whichprovides drug or electrical stimulation to a neural, vagal-nerve, orother anatomical target. The IMD may be partially implanted, such as animplanted insulin pump/delivery system with an external reservoir.Notification (or alerting/alarming) occurs by way of an internal alarmsystem within the IMD and/or an external alarm system which may comprisean external, pager-type device, a patient programmer, and a remotestation where patient data may be sent for review. The IMD communicateswith the external alarm system using wireless communication signal aslong as the external alarm system is within range. The external alarmsystem of the current invention has capabilities equivalent to thosedescribed by Fischell et al in U.S. Pat. Nos. 6,112,116, 6,272,379 and6,609,023. For example, the external alarm system may provide one ormore types of visual, sonic and vibratory alerting signals, and mayprovide voice/data communication between the IMD/patient and a remotemedical monitoring station.

The IMD and/or the external alarm system may provide a single type ofalarm. Alternatively, at least two types of alarms may be used (“twostage alerting”). In one embodiment a major/critical event alarm (an“EMERGENCY ALARM”) can provide notification of the detection of aserious medical event (e.g., a heart attack which is an AMI) and theneed for immediate medical attention, and a less medically significantalert (a “SEE DOCTOR ALERT” or alarm) can signal the detection of a lessserious condition that is not life threatening such as exercise inducedischemia or the detection of a depleted battery. The two types ofalerting consist of different multimodal alarm patterns, which areselectable to occur at different strengths. When a particular sensorymodality of alerting is used to provide notifications of different eventtypes, the signals may differ in amplitude (e.g., strength of signal),pattern (e.g., long or short bursts, inter burst-interval), or frequency(e.g., a 500 or 2000 Hz sound). It would be helpful to perform variousback-up/compensatory operations if the internal and external alertingdid not occur as expected and to be able to quantify and detect theseoperational deviations. Transducer malfunction can cause normallydistinct types of notification to be mistaken, or ignored, by thepatient.

US patent application 2009/0072768, entitled “Use of an accelerometer tocontrol vibration performance” to Murray et al. teaches using anaccelerometer to measure the performance of a vibration motor and toincrease, in a closed loop manner, the voltage applied to the drivecircuit to compensate for changes in the speed of rotation that mayoccur over time. U.S. Pat. No. 6,774,769 to Okada entitled “VibratingAlert Device” describes a method of increasing the voltage applied to avibration alarm so that it increases gently over time and does notstartle a user of the device.

SUMMARY

The invention provides systems and methods for assessing alarmcharacteristics related to medical notification. Alarm occurrence andcharacteristics of the actual transduced signal are measured objectivelyand automatically using alarm tests. This is especially relevant forimplanted devices with vibration alerting. Device operation, includingthe alerting operations, can be adjusted as a function of alarm testresults. Adjusting alerting operations can include assessing,controlling, or adjusting the operation of a vibration alarm of animplanted medical device, and also modifying the alerting operations ina manner that includes or excludes the use of vibration alerting.

A first aspect of the invention includes an implanted medical devicehaving monitoring, detection, memory, communication and alertingcapability. The alerting capability can be internal, external, or both.In the case of internal alerting the invention includes a vibrationalarm capable of providing various patterns of vibration. Both internaland external alerting signals can be evaluated using alarm tests.

An alarm testing system can include a sensor (e.g., an accelerometer)that can sense a characteristic of a transduced alarm signal (e.g., inthe case of a vibration signal the speed, displacement, amplitude,frequency, rise, or fall of the vibration may be measured). A processorcan be configured for deriving and analyzing alarm test results. Thealarm test results can include comparisons between the alarm test dataand alarm test threshold criteria which can be used to determine if thealarm test yielded an ‘alarm-pass’ or ‘alarm-fail’ alarm test result.The processor is further configured to operate according to the alarmtest result.

Alarm tests can be designed with relatively short test signals. Avibration test signal can be quick (e.g., 20 ms or less) so that this isunlikely to be noticed by the patient. Alternatively, the alarm testsignals can be relatively long (e.g., 100 msec) which may occur atcertain times of day, and which may be noticed by the patient in orderto provide assurance to the patient that the device is working. Back-upalarm protocols are provided for instances in which an alarm test fails.

Performing periodic vibration alarm tests may decrease the risk that amotor component will reside continuously in a particular position andbecome biased against movement away from that position. The alarm testsprovide periodic exercise for the transducer.

The described invention addresses the shortcomings of medicalnotification systems that do not monitor or test the notificationtransducers, and offers novel advantages by providing: objective andautomated testing of the integrity of transduced alarm signals;objective quantification of the strength of the alarm signals; alarmtest criteria that are adjusted based upon the programmably selectedcharacteristics of the alarm; objective determination of whether analarm occurred at a particular time and as intended in response todetection of medically relevant events; objective assessment of thetypes of changes in an alarm signal which may have occurred;programmable and selectable alarm back-up and alarm compensationoperations; alarm back-up protocols which are initiated if an alarm in aparticular modality experiences alarm failure. Further the inventionprovides the advantage, particularly relevant for vibration alerts, oftesting an alarm transducer in a manner by which the patient does notbecome aware of this test.

These and other objects and advantages of the current invention will nowbe described in the description of the figures, the detailed descriptionof the invention, and the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a system for medical monitoring and for alerting apatient and/or remote monitoring station that a medically relevant eventhas occurred.

FIG. 2 is a schematic diagram of the components of an example embodimentof the implanted medical device.

FIG. 3 illustrates an oscilloscope screen with tracings obtained duringan example of an alarm test which used an accelerometer to measurevibration, and also has a superimposed trace of the accelerometeroutput.

FIG. 4 shows the 3 graphs of data collected from the accelerometer forthe X, Y, and Z axes during an alarm test for vibration using a 40 mstest signal.

FIG. 5 shows Table 1 which includes a summary of data collected from theaccelerometer for the X, Y, and Z axes during an alarm test forvibration where the alarm test signals ranged from 10 to 40 ms. Table 2shows results for alarm test signals ranging from 5 to 20 ms.

FIG. 6 shows 4 rows of data collected from the accelerometer for the X,Y, and Z axes during alarm tests for vibration using test signalsranging from 5 ms (top row) to 20 ms (bottom row).

FIG. 7 is a flowchart of a method for performing an alarm test andoperating according to an alarm test result, according to an exampleembodiment of the present invention.

FIG. 8 is a flowchart of an alternative method for performing an alarmtest which uses baseline data derived from pre-vibration and/orpost-vibration data, and operates according to test results, accordingto an alternative example embodiment of the present invention.

FIG. 9 is a flowchart of an alternative method for performing an alarmtest which specifically uses a sub-threshold pulse of 10 ms, andoperates according to test results, according to yet another alternativeexample embodiment of the present invention.

FIG. 10 illustrates the components of an exemplary medical monitoringsystem in which the alarm testing can be realized and which in thisexample is the Guardian™ monitoring system.

FIG. 11 is an example of an alarm test programming screen which ispresented to a medical professional in order to configure and calibratethe alarm testing that occurs in the device.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an example of a medical system 20 including internalcomponents 14 and external components 16. The IMD 3 includes sensors tomonitor a condition associated with a patient. For example, electrodecontacts can act as sensors to measure cardiac activity, neuralactivity, or other electrical activity of the body. A microphone sensorcan measure sonic data related to the patient (e.g. cardiac orrespiratory sounds), an accelerometer can measure movement, accelerationor position, and a biosensor can measure metabolite levels within thepatient. In one embodiment, an insulated electrical wire lead 2 caninclude sensors, and can connect with the IMD 3 using an IS1 connectionto communicate with battery-powered sensing electronics contained withinan IMD housing 10. The lead 2 can be configured with sensing electrodecontacts 4 and 5 which can be placed subcutaneously or within the heart.Each lead may incorporate one electrode contact or as many as sixteencontacts. Housing contacts 8 and 9 could be situated within the surfaceof the IMD housing 10 without any wire leads extending from the IMD 3.The IMD 3 can include a stimulator realized as an insulated electricalwire lead 1, having stimulation contacts 6 and 7, which communicateswith battery-powered stimulation electronics of the IMD 3. Contacts 8and 9 (as well as 4, 5, 6, and 7) can be configured to providestimulation, sensing, or both. Stimulation can also be used to providean electric tickle for alerting purposes.

In one embodiment the lead 2 in FIG. 1 could contain a sensor that isadvantageously placed through the patient's vascular system and into theapex of the right ventricle in order to monitor cardiac activity. Thelead 2 may have a sensor attached to contact 5 such as a pressure oroptical sensor which is implanted to sense signals from the digestivesystem in order to monitor activity related to digestion. The sensorcould also be a glucose sensor that is used to measure glucose levels ofa patient, or an electrode that is placed in a patient's brain in orderto sense neural activity. When the contact 5 is configured with asensor, lead 2 has independent wires for communicating power and databetween the sensor and the circuitry of the IMD 3.

FIG. 1 also shows external equipment 16 that consists of: 1. aphysician's programmer 18; 2. an external alarm system EXD 20 which maybe implemented as a pager-type device, a desktop unit, or both; and, 3.a 3^(rd) party such as a remote medical center 22. The physician'sprogrammer 18 has 2-way wireless communication 26 for communicationbetween the programmer 18, the IMD 3 and the EXD 20. The externalequipment 16 provides users with the capability of interacting with theIMD 3, for such operations as programming and retrieving data from theIMD 3. The external equipment 16 also provides external alarm signalswhen the IMD 3 notifies the external equipment 16 that an alert shouldbe issued.

The programmer 18 shown in FIG. 1 can be used to program the IMD 3 inorder to adjust parameters and information related to, for example, datacollection, event detection, data storage, alerting protocols, and alarmtests. The programmer 18 can send a wireless signal 64 to the IMD 3 andit can also receive an incoming wireless signal 63 sent from the IMD.The programmer 18 has an alarm test module 24 which providesfunctionality related to alarm testing. The alarm test module 24 can beconfigured to command the IMD 3 to perform an alarm test and to returnthe test results. For example, the IMD 3 could be told to perform avibration alarm test for 100 ms at a particular vibration level and avibration parameter (e.g. amplitude) could be measured. This value couldbe sent to the programmer 18 as an alarm test result. The test resultsreceived by the programmer 18 can be processed by the alarm test module24, such as by comparing the test result to an alarm test criterion tosee if the test passed. The alarm test module 24 can also create analarm-test event log(e.g., alarm test parameters and results) which canalso include historical alarm test information that was uploaded fromthe patient's IMD 3. This log will contain both alarm test results fortests initiated by the programmer 18, as well as tests done duringnormal operation of the IMD 3, and this information will be codedappropriately. Examples of the alarm tests initiated by the alarm testmodule 24 are shown in FIGS. 7-9, where the alarm test condition triggeris the command sent from the programmer 18. The alarm test module 24also has software routines that provide the medical professional with aninteractive graphical display for viewing and or measuring alarm testresults (e.g. a cursor which can measure a characteristic of a waveformproduced as part of an alarm test such as seen in FIG. 4) and forprogramming the IMD 3 with alarm test parameters such as test times orintervals and the test signal characteristics. The alarm test module 24also permits medical professionals to adjust protocols stored in thealarm test module 28 of the EXD 20, alarm test module 30 of a 3^(rd)party such as remote medical services 22, and alarm module 120 of theIMD 3. For example, protocols can be adjusted to set parameters for theback-up alarms that occur if a particular alarm signal is not transducedsuccessfully. The alarm-test module 28 of the EXD may be provided withsome or all of the features described for the alarm-test module 24 ofthe Programmer 18. Additionally, the two modules 24 and 28 may operatejointly and are configured with routines that allow these modules tosynchronize or update each other's information and parameter settingswhen this is defined as part of an alarm-test protocol or as implementedby a medical practitioner or other user who operates the devices 18, 20.The remote medical station 22, may run software routines which allowremote interfacing with the two alarm-test modules 24, and 28 in orderto obtain information or set parameters as may be required by anindividual patient's monitoring needs. The remote medical station cancommunicate with the alarm module 120 of the IMD 3 directly, but willusually do this indirectly through communication with devices 18, 20.

In FIG. 1, the EXD 20 has a patient operated initiator module 32 whichcan provide a button that allows for the initiation of communicationbetween the EXD 20 and the IMD 3, an alarm disable module and button 34,a panic module and button 36, an alarm transceiver 38 with communicationand drive circuitry, a speaker 40, a visual display system module(“VDS”) 42, a vibration module 44, and a communication circuit 46 suchas can be used to provide near-field and far-field wirelesscommunication (e.g., Zarlink, cellular, line-based modem). Thecommunication circuit 46 allows data transmission to and from medicalservices 22 via the communication link 48. The EXD 20 has a sound inputmodule 50 having a microphone and associated electronics for providing(along with the alarm transceiver 38 and speaker 40) two-way voicecommunication with remote medical services 22. The sound input module 50is also configured to measure the sound emitted by the speaker 40 inorder to ensure that the sound level is within specified bounds as partof an alarm test for the sonic alarm.

The VDS 42 of EXD 20 may include 1 or more colored diodes which areactivated when a particular alarm type is triggered. The VDS 42 may alsoinclude a display screen for displaying waveforms related to senseddata, graphical and text fields related to the functioning of the IMD 3or EXD 20 or information about what caused an alarm. The VDS 42 mayinclude a navigation button which can be used to navigate through menusand to select desired menu options presented by the VDS 42.Alternatively, the VDS 42 may contain a touch-sensitive display screenwhich allows for user input. The VDS 42 can cooperate with the alarmtest module 28 to present the user with options which allow the patientto perform alarm testing of the IMD at will. If the patient places theEXD 20 within range of the IMD 3 and initiates and alarm test, then theEXD 20 will send a wireless command to the IMD 3 to perform an alarmtest such as is shown in FIG. 7. When specified in an alarm-testprotocol stored in the alarm module 120 of the IMD 3, the IMD will thencommunicate the results of the alarm test back to the EXD 20 and thesecan be analyzed, stored, or displayed by the VDS 42 in collaborationwith the alarm test module 28. Upon receiving alarm test results the EXD20 can emit a sonic or visual message of test success (e.g. 2 beeps of1500 Hz, 3 seconds of a blinking yellow LED, or a text messageindicating “alarm test passed”) while in the case of alarm test failurethe alarm test module 28 will cause the EXD 20 to display messages, ordo other operations, as defined in an alarm-test protocol for analarm-test fail result.

The alarm test module 28 of the EXD 20 is capable of performing an alarmtest within the EXD 20 itself. If the alarm test is for a vibrationalarm then the alarm test data can be collected by an accelerometer or amicrophone of the vibration module 44, if the alarm test is for a sonictest then the test data will be collected by a microphone of the soundinput module 50. A visual alarm test can be performed by a light sensorplaced adjacent to the VDS 42 such as the LEDs. Each modality should betested in the Case of the EXD 20 since some of the alarm modalities maynot work well in all environments. If the patient is hard of hearing oris listening to the TV loudly then the visual cue may be the first alarmsignal that is noticed by the patient.

If an alarm notification is sent from the IMD 3 to the EXD 20, via the 2way communication modules 46, 118 then the alarm transceiver 38 canprovide alarm signals 52A-C to the loudspeaker 40, the VDS 42, and/or avibration module 44 to warn the patient that an event has occurred.Under the control of the EXD processor 54, the alarm transceiver 38provides the alarm signals as defined in the alarm protocols of thealarm module 60. In this manner, notification is provided and patientinput responses, or other operations, which occur in response to thealarm are managed. Examples of external auditory alarm signals 51include a periodic buzzing, a sequence of tones and/or speech which maybe a pre-recorded message that instructs the patient as to what ishappening and what actions should be taken or which may be real speechcommunicated by medically trained practitioners at the remote station22.

When the detection of a life threatening event (e.g., AMI ortachycardia) is the cause of the alarm, the EXD 5 could automaticallynotify medical services 22 that a serious medical condition has occurredand an ambulance could be sent to treat the patient and to providetransport to a hospital emergency room or catheterization clinic. Ifcommunication with medical services 22 occurs, the message sent over thelink 48 may include at least one of the following types of informationas previously stored in the memory provided within the EXD's processor54 or as directly uploaded from the IMD 3: (1) What type of medicalevent has occurred, (2) the patient's name, address and a brief medicalhistory, (3) a GPS coordinate and/or directions to where the patient islocated (using the GPS satellite or cellular grid information as per GPSmodule 56), (4) patient data, historical monitoring data, and the datathat caused the alarm (5) continuous real time data as it is collectedafter the alarm, and (6) alarm test protocol parameters and test resultsfor the IMD 3 or EXD 20.

The processing modules 84 and 100, of the EXD 20 and IMD 3 contain areal time clock or timer and other components which are normallyavailable in the processing modules of current art implantable devices,portable smart-devices and pagers. Further, in a preferred embodiment,the EXD 20 is realized using a smart-phone (e.g., as made by Apple,Blackberry or Palm), which may be implemented using specialized softwareand/or smartcards. The individual modules may be implemented in hardwareor software and contains all of the necessary components to implementalarming of the patient and/or remote station. When the EXD is realizedusing a 3^(rd) party device, the keyboard or other buttons can beassigned to operate identically to input means provided on a specializedEXD 20 device.

The patient operated initiator module 32 provides useful capabilities.For example, by pressing a particular button of the initiator module 32(or navigating to a menu item of the VDS 42), the patient can initiatethe transmission of data from the IMD 3, through the EXD 20, to amedical practitioner at the medical services 22. This can allow apatient to selectively choose and tag data in the IMD which is then sentto a medical practitioner. For example, the patient can be told to pressa button to send data when the patient experiences a particular symptomsuch as dizziness. The alarm disable module and button 34 can be used bythe patient to turn off an actual alarm of the IMD 3 and/or EXD 20.After and alarm signal is stopped by the patient, reminder alarm signalscan be issued periodically to remind the patient that an alarm occurred.The patient might press the panic button 36 in the event that thepatient feels that he is experiencing a severe medical event even in theabsence of IMD 3 or EXD 20 alarm notification. The EXD 20 may use acharger 62 to recharge a rechargeable power supply 58 of the EXD 20.

The components of system 20 are configured to cooperate in order toenable alarm testing to occur. The IMD 3, EXD 20, physician programmer18, and remote monitoring station 22 are designed to provide the alarmtesting to occur and the results to be reported and evaluated so thatalarm test results may guide operation of the system 20 in the casewhere alarms are not transduced as intended. Each component of thesystem 20 has an alarm test module which allows it to participate inalarm testing in order to provide this functionality to the system 20.

FIG. 2 is a block diagram of an embodiment of the IMD 3 shown in FIG. 1.The IMD 3 includes a processor module 100 which is powered by a powermodule 102, having a power supply that may be rechargeable and containmeans for receiving inductive charging. The modules of the IMD 3 arefunctionally connected so that communication and power is providedthereby allowing monitoring, patient alerting, and/or therapy to occurunder control of the processor module 100. The processor module 100operates the sensor module 104 to obtain sensed data from sensors suchas provided by lead 2. Sensed data can be amplified and conditioned bythe analog-to-digital (ADC) circuitry 106 and may be further conditionedby means of digital-signal-processing (DSP) circuitry 108. The processormodule 100 can also process the sensed data and then measure selectedfeatures of cardiac data (e.g. R-wave height, average ST-segmentvoltage, ST-segment duration). The processor operates the stimulatormodule 110 in order to stimulate the patient. Lead 1 could be operatedto provide cardiac pacing or defibrillation. The stimulation signal canbe created by signal-processing (SP) circuitry 112, which may include anarbitrary function generator, and can then be amplified by thedigital-to-analog (DAC) circuitry 114. The processor module 100 can usethe memory 116 to store raw, feature, and summary data and an event log.The event log can contain times of events that are detected by theprocessor. The log can further contain various relevant events such asalarm test results. The memory 116 may be accessed by the processormodule 100 in a manner that allows it to function as a query-capabledatabase. If the processor module 100 analyzes the sensed data anddetects a medical event which has been defined as requiring patientnotification, it may do so as defined by the alarm module 120.Notification may include operating the communication module 118 toattempt to communicate with external devices. The communication module118 permits 2-way communication between the IMD and external devices andis configured for both near field and far field (e.g. Zarlink)communication.

If an event occurs for which notification is needed, the processormodule 100 will utilize the alarm module 120 in order to select theassociated alarm protocol for the particular event. If the alarmprotocol uses a vibration component, the vibration alarm module 122operates its drive circuit 124, to power a motor 126 and cause movement(e.g., rotation). The motor 126 may be either an AC or DC motor and thedrive circuit 124 can utilize a frequency generator, voltage gate, orother electronic means in order to generate the alarm signal that drivesthe motor. The drive circuit 124 may also contain circuitry configuredto measure the impedance of the motor 126, either instantaneously, atone or more particular defined moments in time, or integrated over time.The processor 100 may determine that the motor is not functioningnormally if the measured impedance/resistance value fails to meet alarmtest threshold criteria defined in the alarm module 120, causing analarm test failure. This may cause the processor module 100 to record anerror message/alarm-fail alarm test result in the IMD memory 116.

The vibration monitor module 128 contains an accelerometer 130 which canbe MEMS-based and which preferably measures motion along orthogonal X, Yand Z axes. Alternatively a piezoelectric sensor (e.g., single-axisaccelerometer, microphone, electret-based monitor, or other sensorcapable of measuring pressure changes) can be used which is capable ofmeasuring a characteristic of the motor's vibration along at least oneaxis. An ADC module 134 samples the output of the accelerometer 130,preferably at 2-4 times the frequency at which the motor vibrates.Preferably, in the case of a 250 Hz vibration, the ADC should besampling at a minimum of 1000 Hz. Filters 132 may be applied to theoutput of the accelerometer 130 if this is an analog output in order toremove energy from frequencies outside the range of interest of thevibration measurement. The filters 132 can also be implemented digitallyon the output of the ADC 134. The resulting digitized waveformrepresents vibration test data and can be used to measurecharacteristics such as the frequency or amplitude of vibration(displacement). Alternatively, measurements can be made upon the analogwaveform without digitization.

Sonic alarms are provided by the sonic alarm module 136 which contains adrive circuit 138 that powers a sonic transducer 140 such as apiezoelectric speaker. Components that may provide this capacity includecrystal and ceramic based piezoelectric diaphragms, piezoelectricsounders, and piezoelectric buzzers such as those provided by MurataManufacturing Co., Ltd or Omega Piezo Technologies, Inc. The soundmonitor module 142 contains a sound measurement sensor module 144 suchas an electret, MEMS-based, carbon-based, or piezoelectric-basedmicrophone. An ADC module 148 samples the output of the speaker 140,preferably at 2-4 times the frequency of the highest tone. However, ifthe sonic signal is 4000 Hz, the ADC may operate at 1000 Hz if itssampling is time-locked to the acoustic signal. In this example every4^(th) peak of a 4000 Hz sign wave carrier will be measured by the ADC.This will provide an acceptable measure of sound pressure level for a 4kHz tone since the aliased energy will fit exactly into the ADC samplingrate wave maxima coinciding with the timing of the samples of the ADCbuffer. Filters 146 may be applied to the output of the speaker 130 orcan be implemented digitally.

Electric tickle alarm capability is provided by the tickle module 150which contains a drive circuit 152 that can include voltage-stepelectronics to increase the voltage (e.g., 3 volts) of the implantedpower system 102 to higher ranges. Alternatively, the tickle module 150can contain a separate power supply module designed to provideshort-duration high-voltage power. This may be realized by a 2^(nd)rechargeable battery which is powered off of the primary power supply102. Use of an electric tickle has been previously described in Fischellet al U.S. Pat. No. 6,272,379. The electric tickle can be delivered bythe housing of the IMD 3 to which the output of the tickle module 150 isdirected, or via electrodes 8, 9 in the housing, or via a subcutaneouslead 1 which has been positioned to provide a tickle warning rather thanto stimulate an area cardiac tissue.

In the medical system 12 multiple types of events can cause patientalerting to occur. Most relevant to medical monitoring, alarms occurwhen the processor 100 detects a medical event in the sensed data thatis defined as requiring an alert. The alert may be provided by thevibration module 122, the sonic module 136, the tickle charge module150, or a combination of these which occur simultaneously, sequentially,as a backup in the case of a particular type of alert failure, or asotherwise defined in the alarm module 120. In addition to, or insteadof, the internal alarm signals provided by the IMD 3, the IMD cancommunicate with external devices 16 in order to provide externalalarming. Patient alerting can occur if the processor determines thatthe power supply is below a specified threshold. Notification can alsooccur if the processor module 100 determines that there is a problem inthe sensed data (bad data quality or unexpected changes in the measuredfeatures). Additionally, patient alerting can occur if the alarmprotocol module 120 determines that an alarm test command was sent fromthe physician programmer 18 or the EXD 20 and was received by thecommunication module 118. During normal operation, alarm tests willusually occur when clock values of the processor module 100 match timesscheduled for alarm testing.

The medical system 12 of the current invention requires at least threeprocesses to occur successfully during patient monitoring: a medicalevent must be detected by the IMD 3, the patient must be notified of theevent through an alarm, and the patient must notice) the alarm (so thatthe patient can understand its significance and respond appropriately).If the medical event is detected but the patient is not successfullyalerted then the device does not provide any benefit. Ensuring thatalarms can occur in the future have occurred, as intended, and providingappropriate operations or backup alarms in the case where an alarmdoesn't occur as intended is realized in the current invention usingalarm tests. Since a primary method of patient alerting uses a vibrationalarm, an example of how this test is performed is now provided.

Vibration Alarm Test:

Alarm testing can be accomplished by the IMD 3 in order to measurevibration characteristics such as the magnitude of a vibration for atest signal. The physical configuration of the IMD motor 126 in relationto the vibration monitor 128 module may vary. The motor and sensor maybe glued to each other or arranged separately within the IMD 3. In thisexample the two components were connected to a circuit board within theIMD 3 via a flexible cabling arrangement. The accelerometer module 130may be connected directly to the IMD 3 circuit board or may reside uponfoam or other dampening material.

The alarm tests which will be described tend to use very short alarmtest pulses, such as between 5 ms. and 40 ms. Providing vibration alertsis one of the largest uses of energy in an implantable device. Usingvery short vibration tests may therefore be of great advantage. Forexample, if the motor was tested for 10 ms once a day, every day of theyear, the total activation time would be 10 ms*365 which is only 3650 ms(i.e., 3.65 seconds). Even if one wanted to test the motor for 100 ms,and for the test to be repeated 4 times each day, then this would leadto a total activation time of 100 ms*4*365 which is only 146 seconds(i.e., little over 2 minutes of vibration per year). An importantadvantage of the disclosed alarm testing is that it can be implementedwithout depleting much energy from the IMD 3 battery 102.

An alarm test may include a single test signal or test results may bederived from a series of test signals. For example, test signals may bepresented once per second for 3 seconds and measured to observerepeatability. While the accelerometer may only measure vibration alongone axis, the one used here (ADXL330) outputs data for all three axes(X, Y, Z) which were sampled simultaneously and digitized at 1 kHz. Thetime of the processor module 100 can be used for triggering the testsignals and the ADC 134 may be interrupt based and synchronized. Thesteps of the test may be executed by the IMD 3 processor 100 as follows.

-   -   1. Enable accelerometer 130 and start 1 ms timer. Timer's expiry        initiates ADC conversion.    -   2. Start reading ADC 134, and extract 8 most significant bits        (MSBs) which are stored in arrays X[N1], Y[N1], Z[N1], where        here N1=120 samples, which are collected for each axis and serve        as a “sample set” of alarm test data. Sample sets can be stored        in the buffers of the ADC 134 or can be sent to the memory        module 116.    -   3. Collect N2 values of the sample set. These are discarded        since the accelerometer circuit requires time to stabilize. In        this case N2 can equal 10 samples, since about 6 ms is needed        for the accelerometer to reach stability after it is activated.        In FIG. 4, the asymptote between time=0 and the vertical bar        labeled “A” shows this warm-up.    -   4. Activate motor 126 with an alarm test signal defined in alarm        module 120 that lasts for N3 ms, which in this case is 40 ms        (period defined between times B and C in FIG. 4).    -   5. Apply brake, such as a reverse polarity signal, after N4 ms        (not done here).    -   6. Finish collection of sample set until the arrays of 120        values are full.    -   7. Stop timer and ADC conversion.    -   8. Repeat again after delay if alarm test protocol is defined to        use more than one alarm test signal.    -   9. Operate processor module 100 to evaluate alarm test results        by comparing alarm test data to vibration threshold criteria        defined in the alarm module 120 to generate an “alarm test pass        result” or “alarm test fail result”.

FIG. 3 shows measurements, as set of captured oscilloscope traces on anoscilloscope screen. As labeled on the left side of the figure, thetraces were related to the data sensed on the motor control switch, thevoltage supply applied to the motor (i.e., the alarm test signal), andthe ADC sampling of the accelerometer output (i.e., sampling times forthe alarm test data). An N3=40 ms pulse served as the alarm test signal.During the period labeled “pre-vibration period the voltage applied tothe motor is zero. During the first 10 samples of the accelerometer ADC(bottom row), the test signal voltage applied to the motor remains off.Since the accelerometer requires 6 ms to stabilize, this leaves the last4 samples to serve as “pre-vibration baseline” reference values(associated with time-period labeled “Base”). The next 40 ADC samplesrecord the vibration during the “Motor On” period where the test signalwas supplied from the drive circuitry 124. These are the “alarm-on” datavalues which will likely produce the largest values of Table 1. Lastlythere are 70 samples collected after the alarm test signal is halted(termed “decay data” values). The actual values for the X-axis that wereoutput by the accelerometer are shown in a plot at the top of FIG. 4,but are also superimposed on the top of the oscilloscope screen (“MotorX-axis Response”) in order to show the relationship of the vibration tothe test signal that was applied. After alarm-test signal termination,the relatively slow dampening of the vibration causes a substantialsignal to be maintained for about 20 msec. This profile may be partiallydue to a slow decay of the power supply as could be due to discharge ofthe capacitor as well as the choice not to apply a break pulse to stopthe motor.

FIG. 4 shows the accelerometer output for the x, y, and z axes in graphs160, 162, and 164, respectively, after 1 kHz ADC. The x-axis of eachplot labels the 120 samples, with 1 ms inter-sample interval, and they-axis scale range has 256 values derived from the 8 bit ADC buffer.Vertical bar “A” shows where the accelerometer functionally comes online(it takes 6 ms to warm up). Bar “B” shows where voltage of the alarmtest signal was first applied to the motor 126. Bar “C” marks thetermination of the alarm test signal. The alarm test data samples thatfall between A and B serve as the pre-vibration reference values. Thevalues between B and C are the motor-on alarm test data. The datacollected from C to the end of the recording are the decay-period alarmtest data. The alarm test signal produced vibration along the x- andy-axes, roughly in similar magnitude suggesting a circular rotation asopposed to linear or elliptical, while the z-axis recorded only slightvibration, as expected.

Several characteristics of the alarm test data can be used to assessvibration including: a. vibration strength which may be measured as themaximum or minimum amplitude or the difference between the two; b.average vibration strength which may be vibration strength measuredacross a particular interval such as for 15 ms prior to end of the alarmtest signal (e.g. time denoted by “C”); vibration rise, which may bemeasured as the time to reach maximum vibration strength from the startof the alarm test signal or the slope as the vibration strengthincreases over a selected period such the first 20 samples; vibrationdecay which may be measured as the time needed for the amplitude todecrease to a specified vibration strength such as 50% of the average“Motor On” value, or which may be measured as the slope of vibrationstrength decrease across a selected interval (e.g., the first 20 samplesafter the motor is turned off); vibration frequency which may bemeasured as the maximum, or average, number of zero crossings across aspecified interval such as a portion of the motor-on interval. Forexample, in the x-axis plot 160, the average frequency from the 36^(th)and to 64^(th) sample (i.e. 28 samples) is computed from the 7 zerocrossings obtained using a 1000 Hz sampling rate. In this case, thefrequency is 250 Hz (i.e., 7*(1000/28)).

FIG. 5 provides alarm test data summaries from three alarm test signals(test pulses of 10, 20 and 40 ms) in Table 1. The full scale value was0-255 (8 most significant bits). “Delta” is a vibration strength measurecalculated in this example as the difference between the maximum andminimum values recorded within each X, Y and Z dataset. Deviations froma mean value represent positive and negative excursions due to vibrationmovement in opposite directions. Due to the particular physicalconfiguration (orientation of accelerometer to motor), the x-axis wasmost sensitive to motor vibrations although only slightly more than they-axis, while the z-axis showed almost not change. In order to provide auseful alarm test, the test pulse sent to the motor must activate themotor “long enough” to produce a delta measure that can be distinguishedfrom a specified strength-threshold criteria value when the motor isworking correctly. When the motor is not activated, the accelerometer“at rest” has a delta which remains under ≦3 for any axis during thepre-vibration Baseline interval (labeled “Base” in FIG. 3). Even using a10 ms pulse signal, a minimum delta of 16 (seen in y-axis) was found.Accordingly all three pulse durations, although very short, were morethan adequate to be used as an alarm test signal during an alarm test.By calibrating the ADC units, the values of 0-255 can be converted intounits of force, displacement, or otherwise, and the alarm tests can becalculated upon these units rather that simple ADC values.

Table 2 of FIG. 5 provides alarm test data summaries from four alarmtest signals (test pulses of 5, 10, 15 and 20 ms) which produced thealarm test data shown in FIG. 6. FIG. 6 shows 4 rows of data collectedfrom the accelerometer for the x-, y-, and z-axes during vibration-basedalarm tests using test signals ranging from 5 ms (top row), 10 ms(2^(nd) row), 15 ms (3^(rd) row), and 20 ms (bottom row). The periodbetween A and B was increased so that the Base interval contained 10(sample 6 to sample 16) rather than 4 values. Although visual inspectionof the top row of FIG. 6 indicates that the 5 ms pulse did not reallyproduce a visually noticeable oscillation, Table 2 indicates that the x-and y-axes delta values were larger than the z-axis delta, as well asthe corresponding intra-axis Base delta values. However, if features ofthe alarm test data such as “vibration frequency” are to be assessed aspart of the alarm test then the 5 ms pulse was likely too short to serveas an alarm test signal given the particular motor and accelerometerused to conduct this type of vibration-based alarm test.

Illustrative Alarm-Test Embodiments

In one embodiment, the cardiac monitoring system 12 for monitoring ahuman patient utilizes an IMD 3 that has a primary patient alertingmeans which operates an alerting module such as a vibration module 122.An accelerometer 130 is configured to sense movement of the device in atleast one direction during an alert-test. Additionally, the device has asensor 5 configured to operate with sensing circuitry 104 for sensingsignals from the patient's heart. The device's processor module 100 isconfigured to detect abnormalities in the signals from the heart, toalert the patient by actuating the primary patient alerting means (e.g.122) following detection of abnormalities in the signals from the heart,and also to perform at least one type of alarm test, which can bedefined in the alarm module 120. The selected alarm test 202 can includeboth actuation of the primary patient alerting means for at least onedefined test interval and also measurement 206 by the processor module100 of alarm-test data sensed 204 by the accelerometer 130 during thetest interval. The alarm test also includes operating the processor 100to detect whether sufficient or insufficient movement of the vibratoroccurred during the test interval 208, and to produce alarm test resultswhich can include quantity measures of characteristics of the movementsuch as magnitude and frequency. The implanted device also contains awireless communications system 118 for communicating with externalequipment 16 which, in turn, has wireless communication circuitry 46designed to receive signals from the implanted medical device. Thecardiac monitoring system also has a secondary patient alerting means(e.g., 136) which is designed to notify the patient when insufficientmovement is detected. The alarm test can be performed at definedinter-test intervals, if the wireless communications system receives a“perform alarm-test command” from the alarm-test modules 24, 28, of theexternal equipment, or can be performed contingently upon the detectionof abnormalities in the signals from the heart, when the actual alertsignal is provided, and in that manner can serve to trigger a back-upalarm when the primary alarm fails 214. The secondary patient alertingmeans can be internal or external, and can include establishing acare-link session accomplished in conjunction with a remote station 22and can include alerting a remote medical professional 22. Sincecommunication with remote stations are a type of notification, the alarmtests can include communication between the EXD 20 and the remoteservices 22, and this can be configured so that the remote services isnotified that the incoming message is simply an alarm test rather than areal event. The schedule for testing communication-based alerting may bedifferent for that which occurs while testing the IMD 3 or EXD 20transducers.

It should be noted that the monitoring system can use an IMD 3 that hasa first internal patient alerting sub-system that generates at least afirst internal alarm signal that can be, for example, a vibrationsignal. As long as at least one sensor is configured to sense actuationof the first internal patient alerting sub-system and a sensor isprovided for sensing data that is used to calculate a medical conditionof the patient, then the system 12 can provide medical monitoring andalso perform alarm tests. The device's processor module 100 or the EXDprocessor 54 is configured to detect abnormalities in the patient'smedical condition, actuate the first internal patient alertingsub-system following detection of abnormalities in the patient's medicalcondition and also perform an alarm test. The alarm test can includeboth actuation and measurement of the first internal patient alertingsub-system during a test interval so that the processor evaluate thealarm test data to detect whether the alarm signal was sufficient orinsufficient. In the case where the alarm signal was insufficient, thenan alarm-test fail operation can occur such as operating a secondarypatient alerting sub-system to generate a second alarm signal whichnotifies the patient when insufficiency is detected in the firstinternal alarm signal. Since the device has a wireless communicationssystem 118 and external equipment 16 with wireless communication 26, 46designed to receive signals from the implanted medical device, thesecond alarm signal can include communication sent to, or from, a remoteparty (e.g., a central station or physician), or both.

Illustrative Alarm Test Protocols.

FIG. 7 shows an example method of operating the IMD 3 to perform analarm test and then to operate according to the alarm test results. Step200 is the initiation of an alarm test by an alarm test triggercondition being evaluated as true. Alarm trigger conditions can include,for example: a “perform alarm test” command sent from an external device16 and received by the communication module 118 of the IMD 3; or, thedetection of the occurrence of a clock time, tick count, or periodicinterval (e.g., 1 month) by the processor module 100 which has beendefined in the alarm module 120 as requiring the performance of an alarmtest. A “perform alarm test” command can also occur if a patientinitiates an alarm test, for example, by pressing an associated buttonon the EXD 20.

In step 202 an alarm test protocol is selected from the alarm module 120according to the type of test condition that triggered the alarm and isperformed under control of the processor module 100 which causes analarm module 122 or 136 to provide an alarm and causes a monitor module128 or 142 to collect and digitize the alarm test data. In step 206 theprocessor module 100 measures features of the alarm test data. In step208 the alarm test data features are compared to at least one alarm testthreshold criterion. In step 208, the processor can evaluate any alarmtest data which is available from steps which can include: evaluating afeature measured in the current alarm test data; obtaining the resultsof comparisons between alarm test data and alarm test criteria; addingor comparing current alarm test data to historical values of alarm testdata; and, computing statistical or trend summaries from the current andhistorical alarm test data. In step 210 one or more operations andcomparisons which occurred in step 208 are evaluated in order todetermine if the alarm test passed or failed.

In the case of alarm test success, alarm test pass operations 212 occur.Alarm test pass operations 212 can include, for example, sending a testpass result to the alarm module 120 and updating the event log in theIMD 3 memory 116. The alarm test event information sent to the event logcan include, for example, the time of the test, the type of test signalwhich was used, the test results which can simply include a pass/failresult or also may include one or more measurements associated with thetest. The alarm test event log stored in memory 116 may retain only themost recent alarm test results or a defined number of prior results aswell.

In the case where the alarm test failed, then alarm test failureoperations 214 occur. Alarm test failure operations 214 can include, forexample: sending a test failure message to the alarm module 120 andupdating the event log in the IMD 3 memory 116. Additionally, especiallyin the case where the alarm test has been defined to occur as part of anactual alarm triggered by the detection of a medically relevant event,one or more further alarm test failure operations which are defined inthe alarm test module 120 can be implemented by the processor 100. Theseoptions can include, for example: 1. Changing the manner in whichsubsequently sensed data is stored in memory; 2. Halting the attemptedprovision of the type of alarm which failed the alarm test; 3. Storingalarm test data, measured features, and the alarm failure time in eventlog; 4. Repeating an alarm test with a different test signal; 5.Operating according to an alarm test failure protocol which continuouslyor otherwise attempts to communicate with the EXD 20 to provide anexternal alarm; and, 6. Providing an alternative type of alarm signal,in a different modality, which has been defined to be used contingentlyupon failure of an alarm test.

Option 1, listed in the foregoing, is advantageous because if patientalerting does not occur correctly then the IMD 3 may run out of memoryfor storing data related to relevant medical events which are detected.Various memory storage strategies can be used such as decreasing theduration of the samples which are collected (e.g., using 5 second ratherthan 10 second electrogram strips when storing samples of cardiac data),changing the protocols related to decimation of data prior to storage,changing protocols relied upon when stored data is over-written to makeroom for new data, etc. Option 6 is an extremely important solution toalarm failure because if the alarm test trigger condition was thedetection of a medically relevant event, then the alarm test willfunction to identify a faulty alarm and will serve to provide a backupalarm so that the patient is notified successfully. The alarm failureoperations can be selected and programmably defined to be based upon thetype of event that triggered the alarm test.

The alarm test can be used to determine if the alarm signal wastransduced successfully by the vibration or sonic module 122,136 and toperform selected operations in the case where the alarm test fails. Analarm test failure may include the fail operation step 214 of causingthe IMD 3 to send a “See Doctor” alert to the EXD 20 and to note thespecifics of the alarm test failure such as test time and test results.

Alarm tests must be able to occur accurately within a medical devicethat has been implanted in an ambulatory patient. Since the alarm testof FIG. 5 was done with an IMD 3 situated on a workbench rather thanusing an IMD 3 which was implanted in a person, possibly the variance ofthe Base period might be larger in actual practice when a patient ismoving around. There are several possible alarm test protocol solutionsthat address the issue of isolating the portion of accelerometer valueswhich are related to patient movement from those related to the intendedmeasurement of vibration signal of the alarm being tested. The followingprotocols utilize different strategies for performing the alarm tests.Features and principles disclosed in each of these protocols can becombined and extended into more complex alarm test protocols.

Stable Baseline Protocol: In this aspect of the invention, the alarmtest protocol can require that the base delta values remain within aspecific range, for example, less than an absolute level such as 10, ora relative level such as 20% of the maximum expected value during thetest, in order for the alarm test to be valid. The requirement can beevaluated in step 208, and if this is the case than a flag can be setindicating that a stable baseline criterion was not met. This flag maycause the test to fail in step 210, and an alarm test fail operationwhich is defined in step 214 causes the alarm test to be redone no morethan a maximum number of times prior to declaring a final failure,causing the alarm test protocol to change, or operating in an otherwisedefined manner. This protocol is also practicable within the alarm-testparadigm illustrated in FIG. 8.

Inter-axis Protocols: Another solution is to use an alarm test protocolthat compares data between different axes. A characteristic of vibrationsuch as magnitude is evaluated by comparing the x- or y-axis delta withthe z-axis delta, which should be low since the z-axis is normallyorthogonal to the motor's vibration. Since patient activity is unlikelyto map only upon a single axis, the differential between the 2 axes islikely to be related to motor vibration rather than specifically topatient movement, and therefore can be used as an alarm test measure. Itmay also be beneficial to compare data relative to the z-axis for otherreasons. As shown in Table 1 of FIG. 5, an increase from 10 ms to 20 msto 40 ms causes increases in x-axis delta of 25 (i.e. 47−22) and 25(72−47), respectively. This is an increase of 114% (47/22) and 53%(72/47) with a doubling of intensity, and an increase to 227% (72/22)over the full range. In the case of comparing the x-axis to the z-axiswhich is used as a reference then the doubling of intensity causes anincrease to infinity for the first step (47−22/5−5), and an increase to2400% ((72/22)/(7−5)) across the full range. These are much largerchanges those that seen when data from within a single axis was used andcompared to a baseline interval of the same axis. Accordingly, in step208, the alarm test threshold criterion may require that an x- or y-axisdelta be a specified amount larger than the z-axis delta.

Sequential Test-Signal protocols: A third type of alarm test protocolcompares alarm test results obtained from two or more different alarmtest signals tested sequentially. If the test signals are the samesignal then the features measured from the two sets of alarm data shouldbe within a specified range in order for the alarm test to avoid beingflagged and result in alarm test failure during step 208. Additionally,if the two alarm test signals are different (e.g. two different alarmstrengths) then in step 208 the difference measured in the in the twosets of alarm test data can be compared to an expected difference suchas the difference reference value obtained from an alarm test done in amedical professional's office after the IMD 3 was first implanted. Thealarm test threshold criterion would be defined to ensure the differencebetween the vibration strength measured in response to the two alarmtest signals of the present alarm test did not differ from thedifference measured at the medical professional's office, by more than aspecified amount.

Illustrative Alarm Test Types

In addition to different types of protocols that may be implemented tohelp ensure that the test results are stable (e.g. over time, withrespect to a particular axis, or during a baseline or motor-on period),different alarm test types can be designed to achieve differentadvantages. The alarm tests can be conducted for different alarmmodalities provided in the IMD 3 or the EXD 20.

Subliminal alarm tests: An innovative feature of the invention is analarm test which the patient does not notice, or which is barelynoticed. This may be desirable so alarm testing does not interfere withthe patient's daily life. One manner for accomplishing this is to use avery rapid alarm test signal. In the case of a vibration alarm test thismay be a voltage pulse that lasts 10, 20, or 40 ms. Further, the alarmtest may be scheduled to occur while a patient is likely sleeping (e.g.,at 2 a.m.). In this case, the alarm test signal may be a pulse with aduration closer to 100 msec. An example of this type of test is shown inFIG. 9. Another type of subliminal alarm test may be realized byperforming the alarm test whenever the IMD 3 provides patient alertingdue to normal monitoring operations, rather than due to a scheduledalarm test. In a preferred embodiment vibration-alarm tests occur usingthe same vibration frequency which is used for providing real alarms tothe patient. Alternatively, the vibration frequency used during an alarmtest may be selected to be a different frequency, such as a frequencyfor which most subjects are less sensitive.

Assurance alarm tests: Another innovative feature is to provide an alarmtest which the patient notices and which occurs regularly in a patient'sdaily life. In the case of a vibration alarm test this can typically bea voltage pulse that lasts 100 ms, a pair of these pulses, or aparticular pattern of pulses. The alarm test can be scheduled to occurevery 24 hours at 12 p.m. (or only on Friday afternoon at 12 p.m.). Whennot corrected, daylight saving may cause this to occur an hour laterduring part of the year, and clock drift of the IMD may cause this timeto shift slightly over time. Patients may like to have this featurebecause it assures them that the IMD 3 is working correctly and also itreminds them what the vibration feels like. Additionally, the IMD 3could produce this vibration if the patient initiates this by operatingthe EXD 20 to send a “perform alarm test” command. Further, in oneembodiment, a diagnostic test is run in the IMD 3 prior to performingthe alarm test, and the test does not occur if there is problem in theIMD 3. In this case, the lack of an expected alarm test can tell thepatient that a doctor visit may be necessary.

Alarm testing, for either subliminal or assurance alarm test types, canbe triggered in step 200 by the EXD 20 sending an alarm test command tothe IMD rather than the IMD 3 being programmed to do this automaticallyrelative to its internal clock signal. One advantage of this approach isthat the EXD 20 clock can be more easily adjusted when the patient istraveling so that alarm tests occur relative to a particular local timeof day.

Quantitative alarm tests: Another valuable type of alarm test is a testthat enables a medical professional to easily determine if the IMD 3 iscapable of providing an intended alarm at an intended strength. Forexample, if the medical professional causes a test alarm signal to occurduring a patient visit, the monitoring modules 128, 142 can measure thestrength of the alarm and can send data and quantitative measurements tothe physician programmer 18 rather than simply a pass/fail result.Because the IMD 3 is implanted it is difficult to objectively measurethe vibration or sound strength using external devices. The strength ofthe alarm as sensed by an external device applied to the patient may notprovide very accurate objective assessment of alarm signal strength andmay be influenced by the amount of tissue between an external sensor andthe IMD 3. Additionally, it may be difficult for a patient or medicalprofessional to simply feel or listen to the IMD's alarms andsubjectively determine that the strength is 10 or 20% lower than itshould be. In the case where a patient may be a diabetic and may haveperipheral neuropathy it may be difficult to distinguish between whenthe patient is having a sensory deficit or when the alarm is not workingas intended. Accordingly, alarm tests which quantify the size of afeature of the alarm data, rather than simply providing a pass/failresult are extremely advantageous in certain clinical situations.

Anticipatory alarm tests: An alarm test may not only indicate thepresent capacity of an alarm transducer to provide an alarm but may alsobe able to anticipate a future failure of an alarm transducer. In thecase of a vibration alarm, for example, the vibration rise time, plateaulevel, decay-time, decay-rate, decay interval required to reach ½ of themaximum vibration strength, as well as average frequency of vibration,and maximum frequency of vibration may all be used as an index ofincreased future risk of alarm failure. Prior to vibration failure, themotor may turn more slowly, or vibration strength may decay faster afterthe alarm test signal voltage is halted, due to increased resistanceencountered by moving parts of the motor. This type of alarm test maycause the alarm protocol to be changed according to an alarm testfailure operation 214. A type of protocol change which can be defined asan alarm test failure operation 214 can include increasing the strengthor duty-cycle which is used to provide vibration pulses during an alert.In one embodiment, this type of increase will not cause the alertpattern to change and should only alter the strength of the vibrationsignal, while in a different embodiment the pattern of the alert signalitself may be altered slightly to compensate for motor-related issues.For example, 200 ms pulses may be increased to 250 ms in order torestore the intended strength of the vibration signal.

Check-up based alarm tests: A further alternative is that the alarmtests can only occur every 6 months, or so, when the patient visitstheir doctor for a checkup. In this case, the alarm test routine can bedefined to occur automatically as part of a device diagnostic routinethat is run at that time, or as part of the data-retrieval routine sothat the alarm test occurs automatically when patient data are uploadedfrom the IMD 3. Additionally, alarm testing can be defined to occurautomatically, as part of the protocol whenever communication isestablished between the IMD 3 and the EXD 20. In this case, the resultsof the alarm test can be communicated to the EXD 20 or physicianprogrammer 18 and are stored with the other information about thepatient which is stored in the physician programmer 18.

Back-up alarm tests: A central feature of the current invention is theability of the IMD 3 to identify if an alarm signal fails to betransduced successfully by the vibration, sonic, or tickle module and toprovide an alternative back-up alarm signal in this case. In manycircumstances, the vibration alarm 122 of the IMD 3 is preferentiallyrelied upon by a patient, over other modalities, due to certainadvantages. Vibration alarms can be felt even when the visual andauditory modalities are flooded with information as may occur if thepatient is in a movie theater or restaurant when the patient alertingoccurs. Vibration alarms offer advantages when the patient is hard ofhearing, when the patient does not wish bystanders to know that thealarm has gone off due to medical privacy or other issues. Internalvibration alarms can be essential when the patient does not carry theEXD 20 near enough for an external alert to be triggered successfully.Other patients may prefer the sonic alarm, at least for certain alarmtypes. The alarm monitoring modules 128 and 142 can determine if thecurrent alarm protocol is not successful and can select an appropriatebackup alarm option so that the patient is successfully alerted.Although a patient may prefer an internal vibration alarm, the back-upalarm may be a loud auditory signal or electric tickle so that thepatient is successfully alerted to a medically relevant event such as aheart attack.

In the case where the patient preference is only for external alarms tobe used and the default alarm is realized through communication module118 which contacts external devices 16, then backup internal alarms maybe used. In one aspect, if the external devices do not send anacknowledgement that they received the alert notification, then theinternal alerts can serve as the backup alarm option. In this case, thecommunication module 118 serves as its own monitor and can determinesuccessful or unsuccessful alerting of external devices 16 via theiracknowledgement of alert notification. Here the incoming communicationdata serves as the alarm test data. The feature of relevance in themeasured data can be, at minimum, an ACK communication sent from the EXD20. In the case of the tickle alarm, a voltage measurement device withinthe drive circuitry 152 can be used to monitor whether the tickle wasdelivered to the patient. Here the alarm test data which is collected instep 204 is a voltage or impedance data measured during the tickle andthe alarm test threshold value might be compared to the integratedvoltage level that was sensed during a specified interval. In step 214operations occur which enable the patient to be notified when a defaultalarm does not occur as intended. In step 214, a back-up alarm protocolchange can not only include changing from a vibration alarm to a sonicalarm, but also can entail increasing the volume of an auditory alarmwhich may have been set relatively low since it was assumed the patientwould also experience IMD 3 vibration during an alert.

FIG. 8 shows another example method of operating the IMD 3 to perform analarm test in which baseline data, which are acquired when alarm testsignals are not presented, are compared data acquired while at least onealarm test signal is transduced. In the case of a vibration alarm abaseline interval of data can be used to assess the difference in theoutput from a monitor module 128 (e.g., an accelerometer in this case)between when the motor is active and passive. If a baseline period isused then this period may be obtained in a short period prior to motoractivation, after motor cessation, or both. However as can be seen inFIGS. 3 and 4, since there is a relatively large post-alarm signal decayfunction that here lasts as long as the activation signal itself, it islikely better to only use the period before motor activation. Step 226may be excluded when an alarm transducer is not actively damped (e.g.via electrical brake). Using values from 2 different axes, in which oneaxis is relatively not affected by the motor's vibration (e.g. thez-axis) while the other is altered by the motor's activity (e.g., the xor y axis) can allow the size of vibration to be assessed without usinga baseline reference. However, in the case of a sonic or other type ofalarm, or when vibration is measured along a single dimension by apressure sensor (e.g. a microphone) then use of a baseline period willbe necessary.

In step 200 the initiation of an alarm test occurs when a triggercondition is evaluated as true. In step 220 an alarm test protocol isselected from the alarm module 120 according to the type of testcondition that triggered the alarm and is performed under control of theprocessor 100 which causes an alarm module 120 to provide an alarm andcauses a monitor module 128 or 142 to collect and digitize the alarmtest data. In step 222 the processor 100 measures features of thepre-alarm baseline data that was collected before the alarm signal istransduced, but after the monitor module has warmed up. In FIG. 3, thisoccurs during the period labeled base and includes 6 samples. In FIG. 6,this would be calculated on samples 6-16, since the base period wasextended to 10 samples in order to get a more stable estimate ofbaseline values. In step 224 M test signals are presented for N ms eachand alarm test data is acquired. If so desired a delay may be providedbetween each of the M test signals in order to cause the transducer torecover from the prior alarm signal, but this is not required. In step226, post-alarm signal baseline data is collected, when specified by thealarm test protocol. Post-alarm baseline data can be obtained after eachof the M test signals for example, when the transducer is activelydamped, when sufficiently long interval is defined between M testsignals, in order to measure a decay function of a transducer, or in thecase of a sonic alarm when the transducer recovers quickly.Alternatively, step 226 may only occur after the last of the M testsignals occurs. In step 228 the alarm test data is evaluated. This mayinclude measuring selected features of the alarm test data, computingstatistical measures from the alarm test data, combining alarm test dataresults, individually evaluating alarm test data from the pre-alarm andpost-alarm baseline periods, and comparing at least one measured featureof the alarm test data to at least one alarm test threshold criterion.In step 228, the processor can evaluate any alarm test data which isavailable which can include: evaluating a feature measured in thecurrent alarm test data, obtaining the results of comparisons betweenalarm test data and alarm test criteria, adding or comparing currentalarm test data to historical values of alarm test data, computingstatistical or trend summaries from the current and historical alarmtest data. In step 220 the results of step 208 are evaluated in order todetermine if the alarm test passed or failed. In the case of alarm-testsuccess, alarm test pass operations 232 occur. In the case where thealarm test failed, then step 234 assesses if a selected number offailures have occurred and either repeats the alarm test by returning tostep 220 or invokes alarm test fail operations 236. The alarm failureoperations can be selected and programmably defined to be based upon thetype of event that triggered the alarm test or the type of failure thatoccurred, or both. In the case of an alarm test failure, the IMD 3 maysend notification to the EXD 20 in step 236. The EXD 20 can beconfigured to respond to the IMD 3 in a number of manners that allowsalarm testing to be customized by a patient or otherwise. For example,the EXD send an alarm-test command to the IMD 3 and ask that it re-runthe test according from step 200, so that two test-failures must occurbefore the EXD 20 alerts the patient to an alarm-test failure. The EXD20 or IMD 3 can be configured to run a sequential set of tests where thealarm-test signal is iteratively adjusted based upon alarm-test resultsin order to adjust for characteristics of the alarm test failure. Instep 234, adjustments are made before returning to step 220. In thismanner, the system 12 can permit a self-calibration and adjustment ofthe IMD alerts such as the vibration alert signal. Adjustments of thealert-signal may also be guided by, or require the approval of, amedical practitioner, which is a step that can be added to variouslocations of the method shown in FIG. 8. In addition, as has beendisclosed, the EXD 20 can allow the patient to adjust the level of thealerts signals used in the IMD 3 and EXD 20. These adjustments may berestricted to a certain range, at least for decreases in vibrationlevel. In any case, when the alarm levels have been adjusted by thepatient, or otherwise, then one or more alarm-test criteria which arerelied upon during alarm-tests must be adjusted in order toappropriately conduct the tests. For example, an alarm-test criterionconducted in step 208 of FIG. 8 may be selected from a lookup tablestored in 116 or 120, based upon the alarm settings which have beenselected by the patient. Accordingly, if a high-strength alarm has beenselected then the criteria that are used during the alarm-test will behigher than those used to test a low-strength alarm level. This allows aback-up alarm, or other alarm-test failure operation, to occur only whenthe alarm-test results are different from those expected based upon thealert-level settings of the device.

FIG. 9 shows an example method of operating the IMD 3 to perform analarm test which is specifically designed to be subliminal, in otherwords, it is unlikely to consciously be noticed by the patient. In step200 the initiation of an alarm test occurs when a trigger condition isevaluated as true, which in this example can be the clock in theprocessor 100 of the IMD 3 indicating that it is approximately 2 a.m.and this time being defined in the alarm module 120 as a time when analarm test occurs in each 24 hour interval. In step 240 an alarm testprotocol is selected from the alarm module 120 according to the type oftest condition that triggered the alarm and is performed under controlof the processor 100 which causes an alarm module 120 to provide analarm and causes an alarm monitor to collect and digitize the alarm testdata. The alarm test signal is a 10 ms square wave pulse that is sent tothe vibration transducer using the full range of approximately 3-4 voltsavailable from the IMD 3 power supply 102. In step 244 the processormodule 100 measures and evaluates features of alarm test data andcompares the calculated value of delta with either intra-axis orinter-axis criteria, or both. Step 244 may include, for example,measuring selected features of the alarm test data, computingstatistical measures from the alarm test data, combining alarm test dataresults, evaluating alarm test data from a pre-alarm baseline period,evaluating a rise or decay function of alarm strength, and comparing atleast one measured feature of the alarm test data to at least one alarmtest threshold criterion. In step 244, the processor can also evaluateany alarm test data which is available which can include: evaluating afeature measured in the current alarm test data, obtaining the resultsof comparisons between alarm test data and alarm test criteria, addingor comparing current alarm test data to historical values of alarm testdata, computing statistical or trend summaries from the current andhistorical alarm test data. In step 246 the results of step 244 areevaluated in order to determine if the alarm test passed or failed. Inthe case of alarm test success, alarm test pass operations 248 occur. Inthe case where the alarm test failed, then step 250 assesses if aselected number of failures have occurred and either repeats the alarmtest by returning to step 240 or invokes alarm test fail operations 252.The alarm failure operations can be selected and programmably defined tobe based upon the type of event that triggered the alarm test or thetype of failure that occurred, or both.

Alarm Test Signals.

The alarm test signals which are used may be pulses, ramps, sinusoids,or other types of signals. Additionally, more than one type of alarmvibration pattern can be tested in alarm tests conducted in a particularIMD 3. If the alert test signal is a voltage pulse that is used to drivevibration then the pulse may be a triangular waveform, or ramped pulsein order to cause the transitions between the on and off state to occursmoothly. If more than 1 alarm test pulse is used, such as may occur ina paired-pulse alarm test protocol, then the pulses can all have aparticular voltage or may have different voltages. When differentvoltages are used, then any non-linear response of the motor which maybe important could be detected. For example, the motor may work well atpeak voltage, but not below that, causing a potential problem as theimplanted battery ages or if non-peak voltages are used in theproduction of the actual alarm signals. If paired pulses are used, andlonger pulse durations are selected as alarm test signals, then thepulse durations and inter-pulse intervals should be different that thoseused during actual alerting so that the test does not produce a patternthat the patient may be more likely to detect. The alarm module 102 maycontain alarm test protocols that cause specified voltage patterns to besent to the drive circuit 106 to cause the motor 126 to vibrate at anintended speed, frequency, or amplitude. When the motor is designed sothat rotational speed is directly proportional to vibration frequencythen the two terms become interchangeable.

Sonic alarm testing can occur for internal or external alarms that usesound. The alarm test signal can occur at lower intensity than soundused for actual sonic alert. One manner of testing transducers is todecrease frequency of the test signal sufficiently that it can besampled by the ADC sampling rate. Accordingly, although a sonic alarmsignal may occur using a 2000 Hz carrier frequency, the alarm testsignal can be 500 Hz.

Threshold Criterion.

In addition to different types of alarm test protocols, various alarmtest criteria can be used to ensure the alarm test is valid and toprovide other advantages. It should be noted that the alarm testcriteria can be selected or adjusted in relation to the settings beingused by a patient. For example, if a patient's doctor has set their IMD3 to use a medium vibration setting for providing notification then thealarm test uses threshold criteria which are set according to thatsetting. If the alarm notification was presented using a high vibrationsetting, then the threshold used by the alarm test would be larger. Inthis way, the settings for individual patients which are relied upon toprovide actual alarms can be incorporated in to the criteria used toevaluate alarm test data.

Test Validity criteria: The alarm test protocol may implement a “featureconsistency requirement”. This type of criterion is helpful to ensurethat the recorded motion is related to the alarm vibration rather thandue to external forces. If this is the case then consecutive maxima orminima of the measured vibration waveform, across a specified intervalshould not differ beyond a specified amount. If this occurs, then thedata can be flagged in step 208, and the test can be redone in step 214by sending operation flow along path 215. It is unlikely that movementthat is not related to the vibration alarm being measured will affectthe accelerometer readings much when test signals of between 10 and 40ms are used since these short intervals would require non-alarm signaloscillatory activity that is over 25 Hz (i.e. 1000 ms/40) to occur,which is much faster than that of endogenous movement of the human bodyor of forces that are normally applied to the human body during dailylife. Test criteria can be applied to the individual maxima and minimarather than to the difference measure “delta” and the criteria can beapplied to sequentially, for example, M number of positive and negativedata values must be above specified set of values which increase ordecrease when the criteria is related to the onset or offset of an alarmsignal.

Paired pulse criteria: When the alarm test uses 2 sequential pulses ofdifferent strengths, separated by a pause, then the increase within aparticular axis may be compared to a paired-pulse intra-axis value andthe difference between these two values must meet a paired-pulseintra-axis threshold criterion. When values from 2 or more axes arecompared then this result is compared to a paired-pulse inter-axis valueusing a paired-pulse inter-axis criterion. Paired pulse designs may beused to examine non-linear characteristics in a motor's performance, orto obtain two estimates when the motor is on and is in two differentstates of motion. When more than 1 pulse is used, then the accelerometerresults for two or more pulses may be combined when evaluating thevibration test. For example, only one pulse can be required to produce achange in the accelerometer that meets a threshold criterion (i.e. themaximum result is used), or all the pulses must all pass the thresholdtest. Numerous variations in the evaluation of test results areobviously also possible.

Age/usage based criteria and criteria correction: Threshold values canbe determined during calibration which occurs at time of manufacture, attime of implantation, or at subsequent calibration periods that areaccomplished during doctor visits or automatically by the device atspecific intervals. Additionally, the thresholds can be adjustedaccording to the amount of use that a transducer, such as a vibrationmodule, has experienced. For example, as the module ages or is used, anexpected change in vibration strength or frequency may occur and onlydeviations from this expected change may cause a vibration-failure eventto occur. An alert-failure event may require that the vibration voltagebe increased by a specified amount. If this is the case then the medicalprofessional may adjust the vibration to the intended level and thenreset the threshold criteria. Alarm test results can be compared tothose obtained during a calibration profile operation which occurseither at the factory, or during an initial patient visit after IMD 3 isimplanted.

Intra- and inter-axis criteria: These two types of criteria may be usedindependently or jointly to create alarm-test results. When the alarmtest uses a single pulse which is compared to a baseline reference valuethen the increase within a particular axis may be compared to aintra-axis threshold criterion, while when values from 2 or moredifferent axes are compared then this result is compared to aninter-axis threshold criterion. An inter-axis threshold criterion mayrequire that that values assessed in the x-axis are within a specifiedrange of those measured in the y-axis, in order to ensure that the motoris providing circular motion. If the two axes produce differentvibration strengths, or if this difference changes over time, then thismay suggest that there is something wrong with the motor.

Alarm-test criteria related to complex alarm-test signals: The alarmtest threshold criteria values may be constant for a single discretedrive signal (e.g. single pulse), for a series of pulses of the sameshape, or may change for series that use different shapes, utilize testsignals having linear or arbitrary functions (continuous ordiscontinuous). Two or more functions can be used as alarm test signalssuch as two voltage functions with two different slopes (e.g. 2× and 4×)and each test signal will be evaluated with a different criterion. Asingle pulse which ramps from 3.0 to 3.6 volts may be used as an alarmtest signal. In some embodiments, a specified voltage will cause themotor to vibrate at a particular speed. DC-motors are often designed toincrease in speed as the DC voltage increases. A voltage by frequency,or voltage by vibration, magnitude function may be derived and assessedwith alarm-test criteria. When AC motors are used, then thecharacteristics of the AC signal, (e.g., voltage, AC frequency) can beused in the evaluation of the resulting alarm test data measurements ofvibration frequency or amplitude.

Overview

The alarm test methods and systems can be incorporated into many typesof implantable, or semi-implantable, medical devices. These can also berealized by independent modules which can be self-powered and which areimplanted separately within a patient. These may be stand-alonealarm-testing modules that monitor alerts created by other devices, orcan be modules that contain both alerting and monitoring capacity andwhich communicate with other medical devices implanted in the patient.Alarm-testing devices can be realized by physically attaching these tothe housing of a medical monitoring and/or treatment device thatprovides patient alerting.

FIG. 10 shows the components of an exemplary medical monitoring systemin which the alarm testing can be realized. In this example, theAngel-Medical Guardian™ monitoring system is shown which has bothinternal and external patient alerting capacity. The left side of thefigure labeled “A” illustrates schematically the Angel-Medical Guardian™monitoring system which can be the medical system shown in FIG. 1. Thefigure shows a patient with an IMD 3 having a lead that is inserted intoa patient's heart. The EXD 20 communicates wirelessly with the IMD 3 andmay also communicate with the physician's programmer using wired orwireless means (in the figure the EXD is shown communicating with theprogrammer by means of a cable). On the right side of the figure, anactual system is shown and includes the IMD, lead, and externalequipment including an EXD and programmer, while a remote medicalcenter, which can be contacted from the EXD via a cellular network, isnot shown.

FIG. 11 shows the type of screen which must be used to configure thealarm-tests in actual clinical practice. This screen is presented to amedical practitioner during the programming of the IMD when the IMD isprogrammed just after implantation or during subsequent visits by thepatient during which data is uploaded from the IMD and the IMD istested. The top of the Screen shows the patient's unique ID which hereis 3418. The screen displays information as to the time the last testwas performed under control of a physician's programmer (which oftenshould be less than 12 months, and preferably at least every 6 months).Because the patient may not go to the same doctor's office on differentvisits, the data on which the last alarm test was performed undercontrol of a patient programmer is uploaded from the event log of theIMD memory 116. While this information is also available in thealarm-test module 28 of the EXD, this is not used to populate this fieldbecause EXDs can be lost and the record in the IMD will be morecomplete. The “Text Schedule” sub-panel allows the medial professionalto schedule the time of day that the alarm-test occurs as well as theday of the week. Although the test can be done less than once per week,Angel-Medical currently prefers that the alarm is tested at least once aweek so this sub-panel is configured for weekly testing. The “TestParameters” sub-panel allows the medical personnel to determine if thetest is performed using a ‘subliminal’ mode, which uses relatively shortalarm test signals, or a ‘patient assurance’ mode which allows thepatient to notice the alarm test. Next to the vibration and soundcheck-box options are drop-down menus that allow the medicalprofessional to adjust, within an allowed range, the specific durationwhich will be used for an alarm test. The “perform test now” buttoncauses an alarm-test to be conducted with the selected parameters andthese parameters and the results are then stored in the alarm-testmodules 24, 28, and the memory module 116 of the IMD. Although the“perform test now” button will allow alarm-testing to occur, the alarmtesting also may occur automatically when the programmer firstcommunicates with the IMD 3 during a doctor's visit, if this is definedin the programmers default communication protocol. The “configure”button will invoke a separate screen in which the alarm test parametersmay be further configured. For instance, in the case of the vibrationalarm test signal the 10 ms test signal can be configured to be repeated2 or 3 times and the results from all repetitions are used to determinewhether alarm test pass or alarm test failure results have occurred. Inthe case of the tone alarm-test, the volume, repetition rate, testfrequencies, and number of repetitions may be configured. The “If afailure occurs during an Alarm Test” sub-panel determines what actionsto take during failure, such as immediately alerting the EXD of such afailure. Additionally, the IMD may revert to a sonic alarm if thedefault alarm is a vibration alarm, or vice-versa, using thecheck-boxes. The “configure” button allows the user to adjust and designmore additional alarm-failure features such as attempting re-testsbefore deciding an alarm test has failed. The “if a failure occursduring actual event” is a sub-panel that determines what to do if thealarm-test fails when an actual alert signal fails to be evoked, forexample, in response to the detection of a medical event. This paneltherefore serves to design the “back-up” alarm. Additional settings maybe adjusted using the “configure” button as have been describedpreviously. The Save button allows the current settings and preferencesto be saved both in the Programmer, the IMD, and the EXD. The “ViewEvent Log” button allows the medical practitioner to view the event logsof the IMD, the EXD, and the Physician programmer. This informationincludes graphs of the historical alarm alarm-test results in order todetermine if the IMD and EXD are functionally correctly and as expected.The “Cancel” and “Help” buttons allow the medical practitioner to canceloperations or view help screens as is conventionally practiced. Theparticular embodiment of the alarm test and backup window shown in FIG.11 is shown for illustration and can obviously include other features,such as allowing for design of the alarm-testing which occurs in the EXD20. However, this is not practiced in the example shown.

The alarm test protocols described here can be implemented by theprocessor of the IMD 3, or may be appropriately modified to be realizedby the processor 54 and alarm test module 28 of the EXD 20. The IMD 3alarm test module 120 can be implemented as an actual module 120 asshown here, or may be realized using the operating program of the IMD 3processor 100 and alarm test parameters stored in the IMD 3 memory 116so that the alarm tests are carried out as intended. The modules of FIG.2 can operate to measure data which is presented in FIGS. 3-6, and canevaluate the alarm test data to realize alarm test results that are thenused to guide operation of the system 12. The methods depicted in FIGS.7-9 may be applied to alarm testing of alarm signals that cue to patientwith visual, sonic, vibratory, pain, or other types of cues, and foralarm related operations that require communication between the IMD 3,EXD 20, physician programmer 18, and remote diagnostic center 22.

The terms “alerting”, “alarming”, and “patient notification” aregenerally used interchangeably in this material. This disclosuredescribes illustrative embodiments which do not limit the invention. Theconfiguration of the system, the number of components, and the functionof the components can be modified and still serve to realize theadvantages of the invention as described herein. The steps of theprocesses and methods may assume a slightly different order withoutdeparting from the intended results which have been described, and loopsfrom later steps to earlier steps may occur at other steps in theprocess. The modules and steps described herein may be implemented bysoftware or hardware since these will produce equivalent results.Although the modules of FIG. 2 are shown as discrete components,portions of modules that perform similar functions may be shared betweenmodules. The titles (e.g., “Overview”) used to name different sectionsof this disclosure are meant for organizational purposes only and arenot meant to be limiting in any manner.

1. A cardiac monitoring system for a human patient including: animplanted medical device including: a primary patient alerting meanshaving a vibrator which includes a drive circuit and motor; anaccelerometer, the accelerometer configured to sense movement of theimplanted medical device in at least one direction; at least one sensorfor sensing signals from the heart; a wireless communications system; aprocessor, the processor configured to detect abnormalities in thesignals from the heart, the processor further configured to actuate thevibrator following detection of abnormalities in the signals from theheart, the processor also configured to perform an alarm test; the alarmtest including both actuation of the vibrator drive motor for at leastone defined test interval and measurement by the processor of alarm-testdata sensed by the accelerometer during the test interval, the alarmtest further including operating the processor to detect sufficient orinsufficient movement of the vibrator during the test interval; theprocessor further configured to operate upon detection of insufficientmovement; and, an external equipment having wireless communicationdesigned to receive signals from the implanted medical device.
 2. Thesystem of claim 1 wherein the operation which occurs upon detection ofinsufficient movement includes operating a secondary patient alertingmeans that is designed to notify the patient when insufficient movementis detected.
 3. The system of claim 1 wherein the external equipment isdesigned to alert the patient following the reception of a wirelesscommunication indicating insufficient movement has been detected.
 4. Thesystem of claim 1 wherein the external equipment is designed to alert aremote party following the wireless communication indicatinginsufficient movement has been detected.
 5. The system of claim 1wherein the operation which occurs upon detection of insufficientmovement includes wireless communication which notifies a remote party.6. The system of claim 1, wherein the processor is further configuredfor transmission to the external equipment of the alarm-test data. 7.The system of claim 1 wherein the operation which occurs upon detectionof insufficient movement includes adjusting the storage of the data,including the alarm-test data, in the device.
 8. The system of claim 1wherein the processor is further configured to perform an alarm testcontingently upon the detection of abnormalities in the signals from theheart whereby the device can assess if an alert signal has successfullybeen transduced.
 9. The system of claim 1 wherein the operation whichoccurs upon detection of insufficient movement includes implementing asonic alarm on the implanted device, whereby the sonic alarm serves as abackup alarm that ensures the patient will still be alerted.
 10. Theimplantable medical device of claim 1 wherein the insufficiency isdetected using an alarm test criterion derived using a calibrationsession, the criterion being stored in the memory of the device.
 11. Theimplanted medical device of claim 1, wherein the alarm test fordetecting insufficiency uses at least one criterion that is set as afunction of which of two or more alarm types is being tested, the alarmtypes including at least a SEE DOCTOR alarm and an EMERGENCY alarm,wherein the alarms have different vibration characteristics.
 12. Theimplanted medical device of claim 1, wherein at least one criterion isset as a function of which of two or more alarm levels are selected, thealarm levels including at least a low level alarm and a high levelalarm.
 13. The system of claim 1 wherein the operation which occurs upondetection of insufficient movement includes adjusting a drive voltagepattern that is received by the drive circuit, such adjusting occurringfor at least one of the following parameters: pulse-width modulation,pulse width, inter-pulse duration, duty-cycle of the “on” period withineach pulse, pulse shape, and pulse frequency.
 14. The system of claim 1wherein the alarm test includes using a vibration alarm test signal witha duration of less than 20 ms.
 15. The system of claim 1 wherein thealarm test includes using a vibration alarm test signal that is selectedto occur when the patient is sleeping.
 16. The system of claim 1 whereinthe alarm test includes using a vibration alarm test signal that isselected occur periodically at a selected time when the patient isnormally awake.
 17. The system of claim 1 wherein the alarm test detectsmovement insufficiency using an inter-axis criterion that compares alarmtest data sensed from a first axis to data sensed from a second axis,and wherein the second axis is relatively orthogonal to the movement ofthe motor.
 18. The device of claim 1 wherein the alarm test uses anintra-axis criterion that compares at least a portion of alarm test datasensed from a first axis oriented along said one direction to datasensed from the first axis during a period defined to serve as abaseline reference.
 19. The device of claim 1 wherein the alarm testevaluates alarm test data using least one of the following measures:vibration strength, vibration frequency, vibration rise, and vibrationdecay.
 20. The implanted medical device of claim 1, wherein theaccelerometer is a microphone which senses acoustic pressuremeasurements.
 21. The device of claim 1 wherein the alarm test usescriteria designed to detect an increased risk of impending futurevibration failure by measuring insufficiency in one of the followingmeasures: vibration frequency and vibration decay.